'It is not clear how much of this revenue was generated from your proprietary-trading business, hedge-fund activity and private-equity funds that would be affected by the Volcker rule', Suzanne Hayes, assistant director of corporation finance at the SEC, wrote in the initial letter. JPMorgan disclosed in a previous filing that it liquidated proprietary holdings within the equities unit and 'it is not clear if this was the extent of your proprietary-trading business', she wrote.

The letters preceded JPMorgan’s assertion in May that a portfolio of credit derivatives, which bet against the creditworthiness of U.S. companies such as Wal-Mart Stores Inc. (WMT), was a hedge against a weakening economy rather than a proprietary bet. The position was amassed by trader Bruno Iksil, who came to be known as the London Whale because his wager was big enough to move the market.